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Machine A and Machine B are each used to manufacture 660 [#permalink]
18 May 2006, 18:34

00:00

A

B

C

D

E

Difficulty:

5% (low)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

Machine A and Machine B are each used to manufacture 660 sprockets. It takes machine A 10 hours longer to produce 660 sprockets than machine B. Machine B produces 10% more sprockets per hour than machine A. How many sprockets per hour does machine A produce

A. 6
B. 6.6
C. 60
D. 100
E. 110

This took me a long time to calculate and figure out. Does anyone have a quick method that you can show me?

Source suggested backsolving due to time constraints.

Using POE, answers C, D and E look too big because the difference in time it takes for A and B is [u]only[/u] 10% and it takes [u]10 hrs more [/u] for A than B to make 660.

Now going by backsolving, start with A (as it's easy one without decimals :-D ).

If A makes 6/hr --> B makes 6.6/hr.
It takes A 110 hrs for 660 sprockets (ot whatever they are) and
it takes B 100 hrs for the same.

B = x hrs to produce 660
A = x + 10 hrs to produce 660

in one hr B produces 660/x
in one hr a produces 660/x + 10
660/x - 660/x+10 = 1/10(660/x+10)
solving we get x = 100
x + 10 = 110...
Thus Aproduces 660/110 =6 sprockets in an hour.

I couldnt think of a faster approach, but the above one dint take much time either.